Merge pull request #2 from paleo13/master

+ add ability to include header .tex files

Author: cboettig

inst/rmarkdown/templates/pnas_article/resources/template.tex

@@ -17,6 +17,10 @@
 \usepackage{longtable}
 $endif$
 
+$for(header-includes)$
+$header-includes$
+$endfor$
+
 $if(pnas_type)$
 \templatetype{$pnas_type$}  % Choose template
 $else$